This invention relates to cameras and, more particularly, to an electromagnetic drive device for controlling the diaphragm or camera shutter aperture opening.
2. Description of the Prior Art
It is known to provide an electromagnetic drive device for use in a camera in which the rotor for driving the diaphragm, or shutter blades, is formed from a synthetic resin and electrically conductive coil patterns are provided on the rotor. Thus, when the coil patterns are supplied with current and are subjected to the influence of a magnetic field from a permanent magnet disposed opposite to the coil pattern, the rotor responds by producing a force according to Fleming's left hand law, that controls the operation of the diaphragm or shutter blades. This force for driving the shutter blades may be expressed by the equation F=B:I:L, in which the force F is directly proportional to each of the strengths of the magnetic flux, by the intensity of current in the coil, I, and the coil length L.
In order to generate a suitable force in these circumstances, it is necessary to make the coil as long as possible. This requirement is usually fulfilled by providing coil patterns on the both sides of the rotor. In this case, the coil patterns on the both of the sides must be electrically coupled to each other.
To electrically connect patterns on the both of the rotor surfaces, according to the prior art, a hole through the wall of the rotor is provided, and either solder is poured into the hole, or an electrical conductor is inserted and seated in the hole with both of the conductor ends soldered.
In order to assemble the electromagnetic drive device, therefore, the rotor formed in the foregoing manner, is positioned between two permanent magnets that establish a magnetic circuit. The rotor, moreover, is affixed to the drive axles of the shutter blades by caulking means. The rotary shafts of the shutter blades also are affixed by caulking means to a common substrate that supports the permanent magnets. The shutter blades are then disposed between this substrate and the permanent magnets upon driving the rotor to an open position.
For this reason, the process of manufacturing conventional electromagnetic drive devices imposes a need for the time-consuming and troublesome steps of pouring the solder into the hole to establish an electrical connection between the coil patterns on the opposite surface of the rotor, or fitting an additional electrical conductor in the hole and soldering it to the coil patterns.
An object of the present invention is to eliminate all the above-described conventional drawbacks.
It is a further object of the invention to provide a rotor for driving the shutter blades which move with respective drive axles that are made from an electrically conductive metal so that with the drive axles mounted in the fixture, the coil pattern on one surface of the rotor is also automatically electrically connected to the coil pattern on the opposite rotor surface.
Another object of the present invention is to make the blades from a synthetic resin so that the drive axles and rotary shafts are integrally formed, while at least one of the drive axles is excluded from the integral forming process and is provided through the substitution of an electrically conductive metal that establishes an electrical connection for both of the coil patterns on the opposite surfaces of the blade driving rotor.